The present invention relates to a device for treating aneurysms and in particular to a device for use in the endovascular treatment of intracranial aneurysms.
Two earlier patent documents disclose similar devices but, because they concern devices for blocking vessels within the patient, are not designed for occluding aneurysms. In particular, U.S. Pat. No. 5,334,210 discloses a vascular occlusion assembly which comprises a bag made of rip stop nylon material so as to prevent the passage of blood. The bag has a predetermined diamond shape and thus would not be suitable for conforming to aneurysms. Moreover, the heavy and non-stretch nature of the material of the bag would make it difficult to steer through fine intracranial blood vessels. No guide wire is provided and the bag is attached and detached by a frictional arrangement.
Similarly, WO96/01591 also discloses a self-expanding vascular occlusion device. A pre-moulded basket of metal fabric is collapsed for passage through a catheter, placed in location by a guide wire affixed to the basket, and subsequently expanded within a channel in a patient""s body. Since the passage of a metallic body is traumatic to patients, the basket moves along the interior of the catheter.
Devices in accordance with the present invention are especially suitable for use with a Guglielmi Detachable Coil arrangement (GD coil as disclosed in Gugleilmi G., Vinuela F., Duckwiler G., Dion J., et al. Endovascular treatment of posterior circulation aneurysms using electrically detachable coils. J Neurosurgery. 77: 515-524, 1992.
Saccular intracranial (cerebral) aneurysms occur when regions of weakness in the wall of intracranial arteries result in the development of balloon-like swellings on the sides of the arteries. They are important because they are prone to burst and cause haemorrhage over the surface of the brain (subarachnoid haemorrhage). This can result in death in over 30% of patients within 24 hours and a further 25-30% will die within the next four weeks without some form of surgical intervention.
Until recently the conventional treatment of cerebral aneurysms was to perform a neuro-surgical operation to place a clip across the neck of the aneurysm, analogous to tying the neck of a balloon. Over the past 10 to 15 years, endovascular techniques of aneurysm occlusion have evolved. The common principle to these techniques is that devices or materials are delivered by a tube (catheter) through the parent artery into the aneursym where they induce clotting of the blood (thrombosis) in the aneurysm and effectively remove it from the circulation. The catheter is generally inserted via the femoral artery in the groin and the procedure monitored by x-ray flurosocopy. The devices therefore have to be manipulable remotely, at a distance of approximately one meter without the help of direct vision. In the mid 1980s, balloons were used, made of latex or silicone rubber, to occlude the aneurysm. The results were poor and the mortality high. The reasons for this were: 1. It is rare that an aneurysm can be perfectly filled with one balloon. 2. If more than one balloon is used, large unfilled spaces must remain in the aneurysm (one sphere cannot be perfectly filled with more than one smaller spheres). 3. Distension of the aneurysm will be the balloon(s) is likely to occur and cannot be seen or measured.
Other workers had greater success using sort coils of inert metal, generally platinum, to pack the aneurysm and induce thrombosis within it. The first coils were xe2x80x98freexe2x80x99 in that they were simply pushed up the catheter into the aneurysm and once out of the catheter they could not be retrieved. This made the procedure difficult to control and hence risky.
In 1991 a major advance in coil technology, the GD coil, was developed and it remains the only accepted device used in the endovascular treatment of cerebral aneurysms. Although essentially simply a soft platinum coil, it differs from the xe2x80x9cfreexe2x80x9d coils in that it is captive and therefore controllable until the user chooses to release it.
The GD coil has proved very successful especially for aneurysms of the posterior intracranial circulation. It is often used in the treatment of aneurysms which are thought to be inoperable by other means.
The GD coil is not without problems, however, and amongst these are:
1. Relatively poor results in large ( greater than 1 cm diameter) or giant ( greater than 2 cm diameter) aneurysms, generally because of a tendency for the coil mass to pack down and for the neck region of the aneurysm to enlarge with time after treatment.
2. Failure of endothelium to grow across the neck of treated aneurysms.
3. Tendency for coils to prolapse out of wide necked aneurysms and obstruct the parent artery.
4. Early (procedural) or delayed (post treatment) rupture of the coils through the aneurysm wall.
The present invention seeks to overcome, or reduce, one or more of the above problems.
WO-A-96/18343 discloses an arrangement with an embolic coil having its own surrounding net. EP-A-0352325 discloses an arrangement comprising inner and outer balloons, either of which may be perforated. WO-A-96/12367 discloses an embolic device in which detachment is achieved by means of a sacrificial link which is susceptible to electrolytic disintegration.
According to a first aspect of the present invention there is provided an arrangement for treating aneurysms comprising a catheter, a bag removably attached to one end of the catheter and with its interior in communication with the catheter, the bag being arranged to be inserted in an aneurysm, and at least one insert characterised in that means are provided for placing the or each insert in the bag with the bag inside the aneurysm and before the bag is disconnected from the catheter.
The bag may be provided with a guide wire to assist insertion of the bag and the catheter. The bag may also comprise one or more marker rings, and the guide wire may have a shoulder which engages one of the rings in the manner of a one-way drive. Thus the guide wire may comprise first, narrow end portion on the end of a second portion in the form of a shaft, the portions defining a step or shoulder therebetween. Alternatively, the second portion may be constituted by a widened section of short extent, e.g. a ball-shaped member on a guide wire of otherwise uniform thinner cross-section.
The material of the bag is preferably flexible and stretchable in the manner of nylon stockings so that it can conform to the interior size and shape of the aneurysm. The material is non-metallic and may be made from natural or synthetic fibre material.
The material of the bag may be such as to encourage clotting or, alternatively, to discourage clotting.
The bag may be provided as part of a kit of parts including a bag, a catheter to which the bag is removably attached, and a guide wire.
According to a second aspect of the present invention there is provided a device for introducing an annular or part-annular member into a patient, comprising a catheter having an element at or adjacent one end thereof, with at least one electrode extending along the catheter to said element, characterised in that said element is connected to said member by two or more spaced struts, the struts being arranged to be removed electrolytically when an electric current is passed through said electrode.
The element on the catheter is preferably also annular or part-annular so that the struts provide a stable arrangement for maintaining the member and the element relatively fixed, e.g. with their planes substantially parallel.